<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <style>
        div {
            width: 200px;
            height: 200px;
            background: #58a;
        }
    </style>
    <title>08_箭头函数实践.html</title>
</head>

<body>

    <div id="ad"></div>
    <script>
        //需求-1 点击div 2s 后颜色变成粉色
        //获取元素
        let ad = document.getElementById("ad");
        ad.addEventListener("click", function () {
            //保存 this 的值
            let _this = this;
            //定时器
            setTimeout(() => {
                //修改背景颜色 this
                // console.log(this);
                // _this.style.background = "pink";
                this.style.background = 'pink';
            }, 2000);
        })


        //需求-2 从数组中返回偶数的元素
        const arr = [1, 2, 3, 564, 67, 8, 4, 144, 67];
        const result = arr.filter(function (item) {
            if (item % 2 === 0) {
                return true;
            } else {
                return false;
            }
        })
        console.log(result);

        const result_new = arr.filter(item => {
            if (item % 2 === 0) {
                return true;
            } else {
                return false;
            }
        })

        //再简化 
        //const res = arr.filter(item => item % 2 === 0 ? true : false);
        const res = arr.filter(item => item % 2 === 0);
        console.log(res);
        console.log(result_new);

        //箭头函数适合于this无关的回调，定时器，数组的方法回调
        //箭头函数不适合与this有关的回调，事件回调，对象的方法




    </script>


</body>

</html>